Tumor metastasis remains a devastating problem for all cancer patients and is the major cause of cancer related death in head and neck squamous cell carcinoma (HNSCC) patients in the US. An important biologic and clinical question is how tumor metastasis and treatment resistance are regulated. One mechanism that can regulate both these processes is epithelial-to-mesenchymal transition (EMT). We have identified the MAPKAPK2 (MK2) pathway as a potential regulator of radiation-mediated tumor EMT. However, it remains unknown what effect MK2 activation has on epithelial gene silencing through DNA methylation; whether MK2 pathway is important for generation of circulating tumor cells (CTCs); and whether MK2 can be used as a biomarker to prognosticate HNSCC patient metastasis-free survival. The objective of this current proposal is to determine if HNSCC EMT can regulate tumor metastasis via MK2 pathway activation. We hypothesize that MK2 activation can increase HNSCC metastasis through epithelial gene silencing, upregulation of CTCs via EMT and serve as a prognostic marker for metastatic or recurrent HNSCC. Our proposed work is focused on two specific goals. First, increase our knowledge of MK2 biology using MK2 wildtype and knockout cell lines (in the presence or absence of radiotherapy) and how it can directly affect the DNA methylome through epithelial gene silencing and EMT gene expression; how MK2 activation can regulate tumor growth, EMT and the production of circulating tumor cells (CTCs); and whether high MK2 phosphorylation levels can prognosticate HNSCC patient loco-regional and distant metastasis-free survival. Second, we have access to a Phase I tested MK2 inhibitor which we will begin preclinical testing of this compound with radiotherapy. The significance of studying MK2 biology will provide a better in vivo biological mechanism linking how tumor EMT can regulate treatment resistance and facilitate metastasis. The overall clinical impact of this work will allow us to develop better treatment strategies aimed at improving tumor control and long-term patient survival. My long-term research goal is to identify the molecular determinants involved in HNSCC metastasis and to identify druggable targets to address this significant problem. This preclinical work will lay the foundation for a future precision medicine trial aimed at stratifying patients who express high MK2 phosphorylation for active intervention with a MK2 inhibitor and radiotherapy.